Polyethylene stabilized with bis-(hydroxyphenyl) propanes



Patented Jan. 20, 1948 POLYETHYLENE STABILIZED WITH BIS- (HYDROXYPHENYL) PROPANES Georgev H. Latham, and Daniel E. Strain, Wilmington, -Del., assignors to du Pont de Nemourssdr'company, Wilmington, Del. a corporation ofDelaware No Drawing. ApplioationFebruary3,1944,

Serial No. 520,954

Claims. (01. 260-94) This invention relates to new compositions of matter and particularly to new compositions of matter comprising normally solid polymers from ethylene. This application is in part a continuation of our copending application S. N. 474,850 5 compounding of rubber, or other suitable millin'g filed February 5, 1943. equipment, and adding agent theretal Instead In the practice of this invention any normally of adding the agent to the polymer in the'solid or solid polymer of ethylene made either by the molten state it can be addedto a solution or processes of U. S. Patents 2,153,553 or 2,188,465 suspension of polymer in an organic Sol r y contacting ethylene with water and a to an aqueous dispersion thereof. Thepolymer Deroxy compound catalyst, preferably a diacyl containing the age t. or t e Solution. emulsion, peroxide or a dlalkyl dioxide, at temperature of or dispersion of polymer containing added agent from 40 to 350 C. and at pressures in excess of c be formed into any desired'shapeatmospheric, preferably in the range of 50 t Through the use of the agents described here- 1500 atmospheres, can b used The polymers f in it has been found that three kinds ofstabilizaethylene correspond in composition substantially tion can be brought about, namely, stabilizato (CH2) I, have molecular weights in ex 1' tion against heat-degradation, against light- 4000, and soften 0r melt between about 100 c, degradation, and against degradation upon outand about 120 C. and their melting point is bdoor exposure. stantially independent of their molecular wei ht, In general, the amount of agent to be added to On the basis of their known structure t wguld the ethylene polymer depends upon the agent be expected that these ethylene polymers o l used, and upon the degree and kind of stabilizashow unusual stability to oxidative and th tion desired. The amount of agent added can degradative agencies. It has been found, howry up to 50% on the weight f the et ylene D0 ever, that when 'these ethylene polymers ar ymer but as a rule it is preferred to use the miniposed for prolonged periods to weatherin agenmum amount required to achieve the desired recles, light or heat in contact with air, they Sho sults. The amount commonly used will vary from severe degradation, as evidenced by los in t 0.1 to 5 parts by weight per hundred parts ethsile strength, elongation, and tear resistance. ylene p It is accordingly an object of thi invention In one form of practicing the invention the ethto provide compositions comprising ethylene polylene polymer is dissolved in a hot organic hydroymers, including its interpolymers, which have carbon solvent, e. g., xylene, and to this solution improved stability. Another object is to provide is added the agent in amount sufficient to give 1% compositions comprising ethylene polymers which thereof on the polymer. These solutions are cast in the form of self-supporting films, molded artion steel plates, the thickness of the film is adcles, fibers. or coatings have improved heat and justed so as to give a dry film of about 1 mil in light stability and improved durability upon tthickness, the solvent is removed by evaporation, door exposure. Still another object is to p ovide and, after drying, the film is stripped from the new compositions comprising ethylene polymers l and as a minor component a substituted phenol, a 40 he examples which follow illustrate the utility polyhydric phenol, an aryl amine, a long chain and the outstanding advantages of this invention. aliphatic amine, a heterocyclic compound c Example 1.A solution of a polymer of ethyltaining annular nitrogen, or a polymeric amino one having an intrinsic viscosity of 0.55 (measnitrogen containing substance. Other objects ti ed as a 0. 5% solution in Xyl ne at 85 will appear hereinafter, and a calculated molecular weight of about 9,200

The above objects are accomplished according was prepared by dissolving 10 parts of the polyto this invention by incorporating into a normalmer in 90 parts of hot xylene. To this solution ly solid ethylene polymer a small amount of an was added a sufllcient amount of the agents listagent such as a substituted phenol, a polyhydric ed in Table I, to give 1% thereof, based on the phenol, in any suitable'manner that will thorpolymer. These solutions were poured over steel This-can .be accomplished in any machine suit,-,

. 2 oughly distribute .itv throughout the polymer..

able for mixing solids, as by millingthe ethylene polymer on heated rolls,such as are used-inthe' Stabilizer Original 500 hrs.

1,000 hrs.

1,500 hrs.

The fade-ometer in which the above exposures were obtained was operated at approximately 100 C. and 100% relative humidity.

Example 2.-A polymer of ethylenewas prepared by contacting ethylene containing 60 parts per million of oxygen with water at a temperature of approximately 200 C. and at a pressure of 1,000 atmospheres. The polymer had a melt viscosity of 0.02. One batch of the polymer was untreated, a second milled with 2% phenyl-betanaphthylamine, and a third with 2% of hydroquinone. Each batch was rolled into sheets of approximately 1 mil in thickness and placed in an oven maintained at 100 C. An atmosphere of air surrounded the products during the treatment. At the end of 4 weeks the products were removed from the oven, molding prepared, and tensile and elongation measurements were made. Original and final values are given in Table II.

Example 3.A sample of polythene was milled for one hour on a small rubber mill, the rolls of which were heated to 150 C. This operation was repeated with the addition in one case of 0.1% dicresylol propane to the polythene at the start of the milling period and in the second case with the addition of .01% t diphenylol propane. Suitable samples for determining power factor were prepared from the milled material. The power factor at 3000 me. was .0011! for polythene milled in the absence oi. stabilizer, 00076 when dicresylol propane was present during the one-hour milling period and .00064 when diphenylol propane had been added.

The tensile strength and elongation measurements described in Examples 2 and 3 were measured on samples 1" long and wide, and all measurements were made in triplicate or more on 8. Scott pendulum type tester using a stretching rate of 20 inches/min. Results of tensile strength are given in lbs./sq, in. and elongations are in per cent to break.

Tear resistances were measured on an Elmendort type tear tester, using 1" square sam- Tea: Resistance Alter iade-ometer 4 pies and starting the tear from the end of a slot in the edge of the dim. Values are expressed in units of grams to tear 2" of film 1 mil in thickness, and represent the average or duplicate or triplicate measurements.

In place 01' the substituted phenols oi the examples there can be used bls(4-hydroxyphenyl) dimethyl methane (diphenylol propane), bis(4- hydroxy 3 methylphenyl) dimethyl methane (dicresylol propane), bis(4-hydroxy-3-chlorophenylidimethylmethane, bis(4-hydroxyphenyl; methyiethylmethane, bis(4 hydroxyphenyl) phenylmethane, bis(4-hydroxyphenyl) dipropylmethane bis(4-hydroxy-3,5-dimethylphenyl) dimethylmethane, 4-hydroxyphenyldimethylbutyl- -methane, 4-hydroxyphenyltriethylmethane, 4-

hydroxyphenyldimethylisoamylmethane, and the like.

Polyhydric phenols, in addition to hydroquinone, useful in the practice of this invention include catechol, resorcinol, pyrogallol (1,2,3-trihydroxybenzene), phloroglucinol (symmetrical trihydroxybenzene), p,p'-dihydroxydiphenyl and the like.

Aryl amines, in addition to those of the examples, which are useful include octyl-phenylamine, octadecylphenylamine, p,p'-diaminodiphenylmethane, triphenylamine, alphaand beta-naphthylamines, decyl beta naphthylamine, dodecyl-alpha-naphthylamine, octadecylbeta-naphthylamine, symmetrical phenyl-naphthyl-ethylene-diamine, symmetrical dinaphthylethylenediamine, diphenyl paraphenylenediamine, and the like.

Long chain aliphatic amine useful in the practics of this invention are those containing at least 8 carbon atoms. Typical members of this class of compounds include dioctylamine, octadecylamine, didodecylamine. octyldecylamine, dodecylamine, dodecyltetradecylamine, dihexadecylamine, tributylamlne, and the like.

Heterocyclic compounds containing annular nitrogen include the pyridines, dipyridyl, quinoline, melamine, and nitrogen bases extractable from petroleum, those obtained from shale, or obtainable by pyrolysis of cottonseed meal. These nitrogen bases are complex mixtures of compounds and may be classified in a general way into aromatic bases, e. g., methylated quinolines and hydroaromatic bases, e. g.. the pyrindacine base CIBHZSN.

The polymeric amino nitrogen-containing substances are derived from ammonia or from monomeric amino nitrogen-containing compounds and are characterized by being substantially insoluble in water and soluble in 2% aqueous acetic acid and/or organic solvents. The amino nitrogen can be primary, secondary or tertiary and can be part of an open chain or of a cyclic structure. These polymeric amino nitrogen-containing substances can be divided into sub-groups as follows:

(1) Resinous reaction products of phenols, aldehydes, and a material from the group consisting of ammonia, primary amines, and secondary amines,

(2) Resinous reaction products oi amino alcohols and a substance from the group of acrylic and alkacrylic acids.

(3) Resinous reaction products of amino (5i Resinous reaction products of diaryl guanidines with aldehydes, especially formaldehyde.

(6) Resinous reaction products of diaryl guanidines with aldehydes, especially formaldehyde, and either a primary or a secondary amine.

(7) Resinous reaction products of aryl amines with aldehydes or ketones. (8) Resinous reaction products of vinyl ketones with either ammonia or primary or secondary amines.

(9) Resinous reaction products of phenols} piperazine, and aldehydes, especially formaldehyde.

(10) Resinous reaction products of dimethylolurea dimethyl ether with amines.

(11) Resinous reaction products of polyvinyl chloroacetate with secondary aliphatic amines.

(12) Resinous reaction products of urea, formaldehyde, and aliphatic primary or secondary amines containing less than 5 carbon atoms.

(13) Reaction products of phenol-lignln with dimethylamine and formaldehyde.

(14) Resinous reaction products obtained by the catalytic hydrogenation, in the presence of ammonia or a primary amine, of ketone group containing resins.

Combinations of two or more of the agents can be added to the ethylene polymer, particularly when stabilization against more than one degradative agency is desired.

The agents of the invention are effective in protecting the ethylene polymers against degradation catalyzed by copper and its compounds.

Because of their excellent stability the ethylene polymers containing the agents of this invention are advantageously used as binders, coatings, and

. impregnating agents in the manufacture of electrical insulating materials. In sheet form the compositions of this invention can be used as condenser plate separators, as separators in storage batteries, and as separators for the layers of coils in transformers, and also as external insulation on all sorts of coils such as are used in electrical machinery, radio, telephone, telegraph, and miscellaneous electrical and electronic apparatus.

In the form of sheets the compositions of this invention are valuable as so-called slot insulation in dynamo electrical machines such as motors and generators. In dynamos the connecting coils are positioned in slots which are formed in the magnetic core and which are lined with suitable insulation. Machines of this type are improved when the coil insulations, the slot lining, or both, comprise the compositions of this invention. The connections between the coils and the so-called end-windings are preferably insulated with the compositions of this invention. The connections between the coils may be covered 'by a sleeve which is preferably composed of the compositions of this invention in order that the sleeve may have the desired flexibility, insulating properties, and permanence. Sheets may be punched into segments of the proper shape as spacers between commutator bars of automotive, aero and like motors and generators for direct current and for alternating frequency currents. Motors of this kind are particularly useful in devices and locations where the machines are exposed to conditions abnormally destru'ctive to conventional insulation.

The compositions of this invention can be extruded about wire orother electrical conductors, or they can be formed into tapes or ribbons and applied about the wire or other electrical conductor.

In the above electrical use the compositions of this invention can be employed as such or they can be modified with such materials as pigments, fillers, parafiin wax, or polymeric materials such as rubber, hydrogenated rubber, polyisobutylene, polystyrene, polybutadiene, etc.

The remarkable stability against heat ofthe compositions of this invention renders them more suitable than unstabilized ethylene polymers for melt extrusion of films, fibers, filaments, and coatings, or for other melt manipulations. The physical properties of objects prepared from ethylene polymers by melt manipulation are infiuenced by the temperature used. Temperatures above 185 C. are preferred, providing that degradation of the polymer can be avoided. Unstabilized compositions suffer serious degradation at such temperatures, even when practical precautions to exclude oxygen from the polymers have been taken. However, the stabilized compositions of this invention are resistant to degradation under these conditions. Such films are useful as unsupported films or in coatings or laminations, while the fibers or filaments can be knitted or woven into valuable fabrics, tubings, etc.

We claim:

1. A composition of matter comprising a normally solid ethylene homopolymer and from 0.01 to 5 parts by weight of a compound selected from the group consisting of diphenylol propane and dicresylol propane.

2. A composition of matter comprising a normally solid ethylene homopolymer and 0.1% by weight of dicresylol propane based on the ethylene polymer.

3. A composition of matter comprising a normally solid ethylene homopolymer and 0.1% by weight of diphenylol propane based on the ethylene polymer.

4. A composition of matter comprising a normally solid ethylene homopolymer and from 0.01 to 5 parts by weight of diphenylol propane per parts of polymer.

5. A composition of matter comprising a normally solid ethylene homopolymer and from 0.01 to 5 parts by weight of dicresylol propane per 100 parts of polymer.

GEORGE H. LATHAM. DANIEL E. STRAIN.

REFERENCES crrnn The following references are of record in the Q OTHER REFERENCES Swallow, Endeavour, vol, 3, pages 26-31 (Jan. 1944). 

